This invention relates to a disc brake having carrier members associated with first and second friction pads in which reaction forces are carried through point contacts into an anchor along first and second planes that are aligned with the radial surfaces on a rotor during a brake application to substantially eliminate lateral forces that may contribute to non-uniform wear patterns in the first and second friction pads.
Disc brakes such as illustrated in U.S. Pat. Nos. 4,044,864; 4,219,106; 4,335,806 and 5,551,537 have an anchor with support surfaces or rails that are spaced apart from each other to receive and guide first and second friction pads toward a rotor during a brake application. In such disc brakes, the first and second friction pads each have a carrier member that is retained in first and second rails on an anchor. Reaction forces developed during a brake application are communicated from the carriers into the anchor during a brake application. While the shape of the carrier member may be different as illustrated in U.S. Pat. Nos. 5,111,914 and 6,039,155 all such carrier members are off-set with respect to a radial engagement surface of the rotor and as a result a moment is generated by transmission of a friction force into the anchor. Even though this moment is small it contributes to uneven force and the distribution of pressure on the friction pad against the rotor that may create noise and ultimately uneven wear of the friction pad.
It is a primary object of this invention to substantially eliminate the introduction of a moment into a carrier member of a friction pad during a brake application by providing for the inline transmission of reaction forces generated during a brake application directly into a support member.
According to this invention, a disc brake has a support member fixed to a housing on a vehicle with first and second rails that align first and second carrier members in parallel planes on opposite sides of a rotor. Friction pads on the first and second carrier members are respectively moved into engagement with first and second radial surfaces on the rotor to develop a brake force that is communicated into the anchor to opposes the rotation of the rotor and thereby effect a brake application. The support member or anchor has first and second projections that extend from the first rail and first and second projections that extend from the second rail. The first projections are located in a first plane that is aligned with the first radial surface of the rotor while the second projections are located in a second plane that is aligned with the second radial surface of the rotor. An initial thickness of the friction pads is continually reduced by wear through the engagement with the rotor during a brake application. Each friction pad is attached to a carrier member and defined by a first inwardly projecting lip on a first end and a second inwardly projecting lip on a second end. The length of each of the first and second inwardly projecting lips is equal to an initial thickness of a friction pads plus one-half the width of a projection that extends from a rail. During a brake application and depending on the rotational direction of the rotor, an inwardly projection lip engages either the first and second projections on the first rail or the first and second projections on the second rail along the first and second planes to-transmit braking forces into the anchor without the introduction of a moment that may effect the uniform application of an actuation force between the pad and rotor and ultimately uneven wear of a friction pad.
An advantage of this invention resides in a carrier for first friction member having a inwardly projecting lip that engages a projection that extends from an anchor in a plane that is aligned with a radial rotor surface such that reaction forces are transmitted into an anchor in a same plane as where the reaction force are generated.
A further object of this invention relates to a carrier member for a friction pad wherein an inwardly projecting lip has a length that corresponds to an initial thickness of a friction pad plus at least one-half the width of a projection that extends from a rail on a rotor such that a reaction force is carried through a point contact with the projection with changes in a thickness of the friction pad.